Hi,
In the HW2W1.m file, you have (W1X,W1Y) and (W1xCI,WlyCL) variables(from HW2_P1_W1.txt). so you want to find the difference between the lines ploted by these two variable sets (x,y). but the problem is that the size of W1X and W1xCl is different.
You can use interp1 function interpolate the data for the 2nd plot. Then you can see the difference between the two plots
WlyCL_new=interp1(W1xCl,wlyCL, W1X)% this calculates the values of all y co-ordinates for W1X x-coordinates
wlxCl_new=W1X
%for finding the difference between the 2 plots at -1, you need to find -1 in W1X
%let it be idx
diff=W1Y(idx)-WlyCL(idx); % this gives the difference between two lines.
hope this helps.